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The IUCN Red List Categories and Criteria: Comparison between versions 2.3 (1994) and 3.1 (2001)

All new assessments and reassessments for publication on the IUCN Red List must use the 2001 IUCN Red List Categories and Criteria. Version 3.1. Some taxa included in the current IUCN Red List have not been reassessed since before 2000 and therefore still use the 1994 IUCN Red List Categories and Criteria. Version 2.3. The table below shows the difference between the two versions of the Red List Categories and Criteria.

IUCN Red List Categories and Criteria 2001 (ver. 3.1) 1994 (ver. 2.3) Red List Categories Extinct (EX) Extinct (EX) (EW) Extinct in the Wild (EW) (CR) Critically Endangered (CR) Endangered (EN) Endangered (EN) Near Threatened (NT) (LR): Least Concern (LC) Lower Risk (conservation dependent) (LR/cd) (DD) Lower Risk (near threatened) (LR/nt) (NE) Lower Risk (least concern) (LR/lc) Data Deficient (DD) Not Evaluated (NE) Criterion A A1: A1: Reduction (CR = ≥90%, EN = Reduction (CR = ≥80%, EN = ≥50%, VU = ≥20%) ≥70%, VU = ≥50%) over past 10 over past 10 yrs or 3 generations yrs or 3 generations where causes of reduction are understood AND have ceased AND are reversible A2: A2: Reduction (CR = ≥80%, EN = Reduction (CR = ≥80%, EN = ≥50%, VU = ≥20%) ≥50%, VU = ≥30%) over past 10 over next 10 yrs or 3 generations yrs or 3 generations where causes of reduction may not be understood OR may not have ceased OR may not be reversible A3: Reduction (CR = ≥80%, EN = ≥50%, VU = ≥30%) over next 10 yrs or 3 generations up to max. of 100 yrs A4: Reduction (CR = ≥80%, EN = ≥50%, VU = ≥30%) over over any 10 yr or 3 generation time period (up to max. of 100 yrs in future) where the time period includes both the past AND the future, AND where causes of reduction may not be understood OR may not have ceased OR may not be reversible IUCN Red List Categories and Criteria 2001 (ver. 3.1) 1994 (ver. 2.3) Criterion B B1: B: EOO (CR <100 km², EN <5,000 EOO (CR <100 km², EN <5,000 km², VU <20,000 km², VU <20,000 km²) AND at km²) or AOO (CR <10 km², EN <500 km², VU least two of a, b or c. <2,000 km²) AND at least two of B1, B2 or B3. a: Population severely B1: fragmented or number of Population severely fragmented or number of locations (CR = 1, EN ≤5, VU ≤10) locations (CR = 1, EN ≤5, VU ≤10) b: Continuing decline in EOO, B2: AOO, habitat, locations or Continuing decline in EOO, AOO, habitat, subpopulations, or mature locations or subpopulations, or mature individuals individuals c: Extreme fluctuation in EOO, B3: AOO, locations or Extreme fluctuation in EOO, AOO, locations or subpopulations, or mature subpopulations, or mature individuals individuals B2: AOO (CR <10 km², EN <500 km², VU <2,000 km²) AND at least two of a, b or c. a: Population severely fragmented or locations (CR = 1, EN ≤5, VU ≤10) b: Continuing decline in EOO, AOO, habitat, locations or subpopulations, or mature individuals c: Extreme fluctuation in EOO, AOO, locations or subpopulations, or mature individuals

IUCN Red List Categories and Criteria 2001 (ver. 3.1) 1994 (ver. 2.3) Criterion C C: C: Population size (CR <250, EN Population size (CR <250, EN <2,500, VU <2,500, VU <10,000) AND at least <10,000) AND at least one of C1 or C2 one of C1 or C2 C1: C1: Continuing decline (CR ≥25% Continuing decline (CR ≥25% within 3 yrs or 1 within 3 yrs or 1 generation, EN generation, EN ≥20% within 5 yrs or 2 ≥20% within 5 yrs or 2 generations, VU ≥10% within 10 yrs or 3 generations, VU ≥10% within 10 generations) yrs or 3 generations) up to max. 100 yrs in future C2: C2: Continuing decline AND at least Continuing decline AND number of mature one of a or b. individuals in all subpopulations (CR ≤50, EN a: number of mature individuals ≤250, VU ≤1,000) OR 100% of mature in all subpopulations (CR ≤50, EN individuals in 1 subpopulation ≤250, VU ≤1,000) OR % of mature individuals in one subpopulation (CR ≥90%, EN ≥95%, VU = 100%) b: Extreme fluctuations in population size Criterion D D: D: Population size (CR <50, EN <250) Population size (CR <50, EN <250) D1: D1: VU only - Population size <1,000 VU only - Population size <1,000 D2: D2: VU only – Restricted AOO VU only – Restricted AOO (typically <100 km²) (typically <20 km²) or number of or number of locations (typically <5) AND a locations (typically ≤5) AND a plausible threat plausible threat Criterion E E: E: Quantitative analysis showing Quantitative analysis showing probability of probability of in the extinction in the wild (CR ≥50% within 10 yrs or wild, up to a max. of 100 yrs (CR 3 generations, EN ≥20% within 20 yrs or 5 ≥50% within 10 yrs or 3 generations, VU ≥10% within 100 yrs) generations, EN ≥20% within 20 yrs or 5 generations, VU ≥10% within 100 yrs)